A man sells each of his $2$ articles for $Rs.$ $99.$ On one he gains $10 \%$ and on the other he incurred a loss of $1 \%$ in the entire transaction. What is his total gain in $\%$?

The cost price of an article is $80 \%$ of its marked price for sale. How much percent does the tradesman gain after allowing a discount of $12 \% ?$

Aditya bought $200$ dozen orange at $Rs.\, 10$ per dozen and he spent $Rs.\, 500$ on transportation. Hesold each orange at $Rs.\, 1$ each. What was his profit or loss $\% ?$

An article is listed at $Rs.\,65.$ A customer bought this article for $Rs.\, 56.16$ and received two successive discounts of which one is $10 \% .$ Find out the other discount in this discount scheme offered by the shopkeeper. (in $Rs.$)

A cash payment that will settle a bill for $250$ chairs at $Rs.\,50$ per chair less $20 \%$ and $15 \%$ with a further discount of $5 \%$ on cash payment is (in $Rs.$)

A dairyman pays $Rs.\, 6.40$ per litre of milk. He adds water and sells the mixture at $Rs.\, 8$ per litre, thereby making $37.5\%$ profit. The proportion of water to milk received by the customers is